1. Field of the Invention
This invention relates to a television receiver provided with a sub-picture function and more particularly to a multi-picture television receiver wherein videos can be displayed by respectively different television standard systems (such as the NTSC, PAL, and SECAM) in a television receiver wherein two pictures of the same size are arranged so as to be able to be displayed.
2. Description of the Related Art
In a television receiver having a function of displaying a main picture and a sub-picture which is separate from the main picture and is a second picture, a television receiver having a function of displaying respectively in substantially the same size a main picture on one side and a sub-picture on the other side by dividing a picture into two parts has been already publicized. Hereafter, for the sake of convenience, the main picture shall refer to a picture which is displayed on the left side of the picture and is on the side out of which a synchronized signal which will be a reference in case the entire picture (both main and sub-pictures) is deflected or the like is taken.
FIG. 17 is a block diagram showing a formation example of a conventional television receiver in which two pictures of the same size are arranged and one of the pictures can be displayed as a main picture and the other can be displayed as a sub-picture.
In FIG. 17, a video signal for a sub-picture is output to a main picture/sub-picture superimposing part 12 through a video/chroma/deflecting processing part (called a V/C/D part hereinafter) 1, A/D converting part 2, data re-arranging part (for writing into a memory) 3, video memory 4, data re-arranging part (for reading out of the memory) 5 and D/A converting part 6. A writing timing generating part 7 adjusting the timing of writing data into the video memory 4 and a reading timing generating part 8 adjusting the timing of reading data, out of the video memory 4 are controlled by a controlling part 9 to adjust said writing timing and reading timing on the basis of a controlling signal from the controlling part 9.
On the other hand, a video signal for a main picture is output to the main picture/sub-picture superimposing part 12 through a V/C/D part 10, A/D converting part 62, video memory 63 and D/A converting part 64. The video memory 63 is controlled in the data writing and reading timing by a memory controlling part 61.
The superimposed video signal is reproduced to be a tri-color signal in a video processing part 13 and is fed to a CRT 14.
The operation of the television receiver wherein two pictures of the same size are arranged so as to be able to be displayed , one of the pictures is made a main picture and the other is made a sub-picture as formed as in the above shall be explained in the following.
The video signal for the sub-picture is video/chroma processed in the V/C/D part 1, is separated and converted to a luminance signal and color difference signal from a composite video signal and is fed to the A/D converting part 2. The V/C/D part 1 separates a synchronizing signal from the composite video signal to produce a horizontal synchronizing signal (WHD) and vertical synchronizing signal (WVD) and feeds them to the writing timing generating part 7.
The writing timing generating part 7 generates an A/D converting timing signal 15, data re-arranging timing signal 16 and data writing timing signal 17 on the basis of the WHD and WVD from the V/C/D part 1 and outputs them respectively to the A/D converting part 2, data re-arranging part (for writing into the memory) 3 and video memory 4.
The A/D converting part 2 converts the video signal for said sub-picture to a digital signal on the basis of the A/D converting timing signal 15 and outputs it to the data re-arranging part (for writing into the memory) 3. The data re-arranging part (for writing into the memory) 3 re-arranges said digital converted sub-picture video signal data rows in the order adapted to writing into the memory on the basis of the data re-arranging timing signal 16 and outputs them to the video memory 4. The video memory 4 writes in the memory the re-arranged sub-picture video signal data rows on the basis of the data writing timing signal 17.
On the other hand, the main picture video signal is video/chroma processed in the V/C/D part 10 so as to be separated and converted to a luminance signal and color difference signal from a composite video signal. The V/C/D part 10 separates a synchronizing signal from the composite video signal to produce a horizontal synchronizing signal (RHD) and vertical synchronizing signal (RVD) and feeds them to the reading timing generating part 8 and memory controlling part 61.
The reading timing generating part 8 generates a data reading timing signal 18, data re-arranging timing signal 19, D/A converting timing signal 20 and main picture/sub-picture switching controlling signal (YS) 11 on the basis of the RHD and RVD from the V/C/D part 10 and outputs them respectively to the video memory 4, data re-arranging part (for reading out of the memory) 5, D/A converting part 6 and main picture/sub-picture superimposing part 12. The sub-picture video data read out of the video memory 4 are read out at a speed about twice as high as the speed in writing and with a delay time (H/2) 1/2 time as long as a horizontal scanning period (1H) so that the sub-picture video may be displayed on half the right side on the CRT. This is because, if it is assumed that the sub-picture video data are written in real-time, in case the sub-picture video data are read out for a time n times (n is a positive real number) as long as the writing time, the sub-picture video will be compressed (or extended) to be 1/n time as large.
In the same manner, the memory controlling part 61 controls the video memory 63 to write and read video data on the basis of the horizontal synchronizing signal (RHD) and vertical synchronizing signal (RVD) from the V/C/D part 10. In case the main picture video data are read out of the video memory 63, the same as in the case of the sub-picture video data, the main picture video data will be read out at a speed about twice as high as the speed in writing so that the main picture may be displayed on half the left side on the CRT.
On the other hand, the re-arranged sub-picture video signal data rows written on the video memory 4 are read out of the video memory 4 on the basis of the data reading timing signal 18 generated by the reading timing generating part 8 and are output to the data re-arranging part (for reading out the memory) 5. The data output from the re-arranging part (for reading out the memory) 5 is re-arranged (returned) to the sub-picture video signal data rows as of before the data are re-arranged by the data re-arranging part (for writing into the memory) 3 on the basis of the data re-arranging timing signal 19 and is output to the D/A converting part 6. The D/A converting part 6 converts (returns) said sub-picture digital video signal to an analogue signal on the basis of the D/A converting timing signal 20 and outputs it to the main picture/sub-picture superimposing part 12.
The main picture/sub-picture superimposing part 12 superimposes said sub-picture video signal converted to an analog signal and said main picture video signal on each other. A superimposed video signal is reproduced to be a tri-color signal through the video processing part 13 and is displayed on the picture of the CRT 14.
The television standard systems adopted today in various countries in the world are largely divided into three kinds of an NTSC system adopted mostly in Japan and America, a PAL system adopted mostly in West Europe and an SECAM system adopted mostly in the old Soviet Union, France and East Europe. Among them, the PAL system and SECAM system are common with each other in respect that the number of scanning lines per frame is 625, whereas in the NTSC system adopted in Japan, USA and so on the number of said scanning lines 525 per frame and is different from the PAL system and SECAM system.
Therefore, in the conventional television receiver having a function of displaying in substantially the same size a main picture on one side of a picture divided into two parts and a sub-picture on the other side, a video of a number of scanning lines different from the number of scanning lines on the main picture has not been able to be displayed on the sub-picture simultaneously with the main picture.